This invention relates to the treatment of disorders associated with damage to the brain. In particular, this invention relates to treatment of disorders by cellular transplantation into a damaged brain.
Stroke is the largest cause of adult disability worldwide. The incidence of stroke is about 1.3% of the US population, and 39.4% of victims show significant residual impairments, ranging from hemiplegia to restricted limb use and speech defects. Approximately 60% of strokes are caused by occlusion of the middle cerebral artery (MCAo), resulting in damage in the striatum and cortex with consequent deficits to sensory and motor systems. There is therefore a substantial clinical need for treatments that reduce or alleviate the deficits.
Typical therapies for stroke are aimed at interrupting the cascade of events that lead to intraneuronal calcium accumulation and cell death, and to provide stimulation through rehabilitation, e.g. physiotherapy, to promote intracerebral reorganisation. However, pharmacological treatments must be administered quickly to protect against cell death that typically occurs within three hours of occlusion. In addition, the therapy based on rehabilitation appears to be limited to a period of 3-6 months after stroke, after which residual disabilities do not undergo appreciable reduction.
There has been much interest recently in the possibility of transplanting new cells into the damaged neuronal system to promote repair and alleviate the disorders. One difficulty associated with cell transplantation is the need to provide clonal cell lines from different regions of the brain. This has proved to be a major difficulty in preparing cells for transplantation. WO-A-97/10329 describes the use of conditionally immortalised pluripotent neuroepithelial cells in the transplantation into the damaged brain. The neuroepithelial cells express a temperature-sensitive oncogene so that they are capable of unlimited expansion under permissive low temperatures in vitro, but cease dividing to develop into mature neural cells on implantation into the higher temperature of the brain (38xc2x0 C). A particular advantage of these cells has been shown to be their ability to develop into site-appropriate neurons or glia, under the control of signals from the host brain, so that problems associated with choosing the correct tissue for transplantation is avoided. It has also been shown that the cells can migrate to the site of damage when transplanted into a region proximal to the damaged site. Therefore, the use of these cells offers a viable alternative to pharmacological treatments for repair of brain damage.
However, although the cells were shown to migrate to discrete areas of damage, focal ischaemia results in extensive damage and it is by no means certain that areas of infarction would provide a sufficiently well vascularised matrix to support the survival of grafted cells.
There is therefore the need for improvements in transplantation in order to provide cells that successfully graft into the adult damaged brain and compensate for the deficits.
It has now been realised that pluripotent cells can successfully repair damage when administered into the side of the brain contra-lateral to that containing the site of damage.
Therefore, according to one aspect of the invention there is a method for treating brain damage comprising administering a composition comprising pluripotent cells into the damaged brain, wherein administration is into the brain hemisphere contra-lateral to that containing the site of damage.
Preferably, the pluripotent cells are neuroepithelial stem cells, in particular, those from the MHP36 clonal cell line, defined herein.
The cells are preferably conditionally immortal. Immortalisation may be achieved by the transduction of a temperature-sensitive oncogene into the cells as disclosed in WO-A-97/10329.
The advantage of administering the cells contra-laterally is that the intact (contra-lateral) region may provide a more tolerant environment for cell grafts, avoiding the inflammatory response at the site of damage which might cause cell rejection.
The cells of the present invention are capable of correcting a sensory, motor and/or cognitive deficit when implanted into the brain hemisphere contra-lateral to that of the damaged part of the human brain. The term xe2x80x9cdamagexe2x80x9d used herein includes reduction or loss of function caused by cell loss. Damage may be caused by any of a variety of means including physical trauma, hypoxia (lack of oxygen), chemical agents, for example, damage may be caused by drug abuse, and disease. The following diseases and pathological conditions are examples of diseases or conditions which result in deficits which may be treated in accordance with the present invention: traumatic brain injury, stroke, perinatal ischaemia, including cerebral palsy, Alzheimer""s, Pick""s and related dementing neurodegenerative diseases, multiple sclerosis, multi-infarct dementia, Parkinson""s and Parkinson""s-type diseases, Huntington""s disease, Korsakoff""s disease and Creuzfeld-Jacob disease. Amnesia, particularly following transitory global ischaemia such as after cardiac arrest or coronary bypass surgery, may also be treated in accordance with the present invention.
The present invention is particularly suited to the treatment of stroke where damage occurs primarily in one brain hemisphere e.g. due to an occlusion in the middle cerebral artery.
By xe2x80x9ccontra-lateralxe2x80x9d it is intended that this refers to the hemisphere of the brain that does not contain the site of damage. Therefore, if there is an occlusion in the left hemisphere, then, obviously, the contra-lateral region is the right, undamaged, hemisphere.
Of course, in some instances damage may occur in both hemispheres, and in these cases the contra-lateral region is understood to be the hemisphere which exhibits least damage.
The term xe2x80x9cpluripotentxe2x80x9d is used herein to denote an undifferentiated cell that has the potential to differentiate into different types or different phenotypes of cell, in particular into cells having the appropriate phenotype for the intended use. The cell type or phenotype into which such a pluripotent cell finally differentiates is at least partly dependent on the conditions in which the cell exists or finds itself.
For use in the present invention the cells should be capable of differentiating into cells appropriate to repair or compensate for damage or disease in the target area of the brain. It will be appreciated that cells for transplantation need not be capable of differentiating into all types or phenotypes of neural cells. The cells may, for example, be bipotent. However, a high degree of potency is generally preferred as this gives greater flexibility and potential for transplantation into different areas of the brain.
Suitable pluripotent cells include those known in the art as xe2x80x9cstem cellsxe2x80x9d and those called or known as xe2x80x9cprecursor cellsxe2x80x9d. In particular, neuroepithelial stem cells are suitable for use in the present invention. However, other cells may also be used. Alternative cells may be those defined as haematopoietic stem cells which may be capable of differentiating into neural cells.
The pluripotent neuroepithelial cells are advantageously, and will generally be, conditionally immortal and may be prepared as disclosed in WO-A-97/10329.
The treatment may be carried out on any mammal but the present invention is especially concerned with the treatment of humans, especially treatment with human cells, and with human cells and cell lines.
To treat a patient it is necessary to establish where damage has occurred in the brain. This may be carried out by any method known in the art, e.g. magnetic resonance imaging (MRI). Once the existence of damage has been established, whether it be in one isolated area or in several areas, treatment by implantation of cells into the contra-lateral region to that of the damaged area may be carried out, again by conventional means. The pluripotent cells may be transplanted at a single site, or preferably at multiple sites, and may be able to migrate to the site(s) of damage and, once there, differentiate in response to the local microenvironment, into the necessary phenotype or phenotypes to improve or restore function.
In addition to administering the cells into the contra-lateral region, it may also be desirable to co-administer the cells into the damaged hemisphere (ipsi-lateral region). Treatment in this manner may promote the improvement or restoration of brain function by different mechanisms.
Without wishing to be bound by theory, it may be that repair following transplantation into the contra-lateral region results from migration of the pluripotent cells into the area of damage, with the reconstitution of local circuits to restore or sustain function. It may also be that the transplanted cells augment spontaneous processes within the intact (contra-lateral) side which attempt to compensate for the damage. If the latter is correct, then it may be unnecessary for the transplanted cells to cross to the side of damage to exert an effect.
It may be possible to promote repair by encouraging the activity of particular regions of the brain. By using passive or active exercise of certain regions, it may be possible to augment the spontaneous processes occurring after transplantation. For example, it should be possible to stimulate particular brain regions by requiring certain tasks to be performed. In doing so, the brain region may generate biological signals that aid repair.
The stimulation of the brain may be visualised using detection techniques such as magnetic resonance imaging (MRI). These techniques can be adapted to permit the patient to visualise the active brain regions, so that, through the process of biofeedback, the patient can stimulate particular regions that may encourage repair.
Preferably, treatment will substantially correct a motor, sensory and/or cognitive deficit. However, that may not always be possible. Treatment according to the present invention and with the cells, medicaments and pharmaceutical preparations of the invention, may lead to improvement in function without complete correction. Such improvement will nevertheless be worthwhile and of value.
The number of cells to be used will vary depending on the nature and extent of the damaged tissue. Typically, the number of cells used in transplantation will be in the range of about one hundred thousand to several million. Treatment need not be restricted to a single transplant. Additional transplants may be carried out to further improve function.
Methods for transplantation of cells into humans and animals are known to those in the art and are described in the literature in the art. The term xe2x80x9ctransplantationxe2x80x9d used herein includes the transplantation of cells which have been grown in vitro, and may have been genetically modified, as well as the transplantation of material extracted from another organism. Cells may be transplanted by implantation by means of microsyringe infusion of a known quantity of cells in the target area where they would normally disperse around the injection site. Suitable excipients and diluents will be apparent to the skilled person, based on formulations used in conventional cell transplantation.
The following non-limiting example illustrates the invention.